In the art of making ductwork for ventilation systems, special design challenges are presented because ducts are generally custom designed for each building in which they are installed. Ductwork includes long, straight three dimensional ducts and shorter three dimensional sheet metal fittings. Fittings are used when ducts change dimensions or direction. Each fitting includes a number of separate two dimensional sheet metal pieces that are cut from two dimensional sheet metal stock and then folded and/or edge-fitted together to form a three dimensional fitting.
In the prior art of which I am aware, U.S. Pat. Nos. 4,551,810 and 4,554,635 (issued to Levine) disclose computerized systems especially designed to aid in the production of customized ductwork by cutting patterns on two dimensional sheet stock, wherein the patterns are for two dimensional pieces that can be fit together to form three dimensional fittings and ducts.
Levine U.S. Pat. No. 4,551,810 notes that patterns for sheet metal pieces can be marked on a sheet of metal on an X-Y table. However, there is no disclosure that the method or apparatus is suitable for use at a job site or that the apparatus is small or compact enough to be contained in a truck or van and readily transported to and from a job site. On the contrary, the Levine method and apparatus is most definitely unsuitable for use at a job site for a number of reasons.
The Levine apparatus is relatively large and bulky, and large production runs are contemplated for use therewith. More specifically, the Levine method and apparatus is designed to layout all the sheet metal ductwork fittings for an entire building at one time. Large amounts of expensive off-line storage--one or more 80 megabyte hard disc drives--are required to store the data resulting from calculations for the fittings for the entire building. Furthermore, relatively long periods of time are required with the Levine device for computing the calculations for the entire building. Even more time is required for each change that is made in just one fitting; for example, a change in one fitting may cause the dimensions of many, many other fittings to be changed in the whole building. In addition, the Levine system is designed to operate primarily in a batch-wise operation and not in a real-time environment. In addition, the Levine apparatus would not, practically speaking, fit inside a truck or van for transport and use at a job site. Furthermore, the Levine device is designed to make patterns for more than one fitting simultaneously. This accounts, in part, for the complexity of the software and hardware necessary to implement the Levine system. On a job site, on the other hand, it would be desirable to provide for patterns for fittings, one at a time.
Because of the purpose for generating layout patterns for large numbers of sheet metal pieces for each computer run, Levine is primarily concerned with positioning the developed patterns in a series of groupings which yield a minimum surface area on stock sheet metal sheets so as to provide for optimum material usage and minimum material waste. Material waste concerns may be important when calculations are made for a whole building, and a production run for fittings is made for a whole building at a time. Digital data is generated to represent the optimum grouping, and the digital data representing the optimum grouping is supplied to an X-Y plotting table. The data is formatted in block format and includes digital data representing the starting point for each pattern in X-Y format and sequential digital data in X-Y format representing the contour of each pattern. Such complexities in data collection and transmission would not be needed if only one fitting pattern were calculated at a time.
Levine U.S. Pat. No. 4,554,635 is primarily directed to methods for creating ductwork pattern groupings in which the groupings are positioned so that all the patterns required for producing a final sheet metal fitting are aligned on a sheet material, such that they can be severed from the sheet material by a single, substantially-straight cut across the sheet material. The economy of cutting motions achieved by Pat. No. 4,554,635 may be desirable in large production runs where fittings are produced for an entire building for a run. However, such economies cannot be utilized at a job site where it is very desirable to be able to make one fitting at a time.
The Levine patents teach a computerized system for aiding a draftsman in designing and drafting a group of patterns for sheet metal pieces that economize in the use of materials. The user of the Levine apparatus is, therefore, contemplated as being a trained draftsman who generally works in the environment of a drafting office, and more particularly, an office equipped with computerized systems.
Levine makes use of standard size sheet metal pieces and optimizes pattern groups to minimize material waste. Levine makes no provision for utilizing waste material that is created in the process.
The requirements at a job site are vastly different from the requirements satisfied by the Levine method and apparatus. For example, at a job site there are generally three persons who work together to design and provide customized sheet metal fittings. First, a "take-off" man studies building blueprints and/or the building itself and arrives at a list of estimated customized ductwork fittings that are needed. The take-off man provides a layout man with the list of fittings, and the layout man then manually takes pieces of sheet metal stock and marks the appropriate pattern for each fitting on the sheet metal stock. Finally, a helper or the like cuts out the pieces according to the laid out pattern and folds the pieces and edge fits the pieces to form the fitting.
Performing the duties of the layout man requires a high degree of skill, and layout men are not in plentiful supply. As a matter of fact, there are relatively few capable layout in the work force. The layout man is generally not a trained draftsman, and his skills and job duties are distinctly different from that of a draftsman. The layout man works at a job site and must take the raw data supplied by the take-off man and then, by following complex mathematical formulas, make two dimensional patterns for pieces on two dimensional sheet metal stock that will result in a properly dimensioned three dimensional fitting when the pieces are fitted together.
Another desirable goal that the prior art does not satisfy is the need for a real-time pattern making at the job site. When a take-off man supplies the layout man with the dimensions of the customized fitting that is needed at a job site, it would be very uneconomical and impractical to have the calculations and patterns made away from the job site and have the fitting delivered to the job site. Too much time would be wasted while workers just waited for patterns or fittings to be delivered from an off site location.
The time wastage factor is very significant at the job site. The time factor far outweighs any small economies that might be obtained by optimizing pattern positioning of sheet metal stock to realize small savings in material when the pieces are cut out from the stock. Thus, the benefits of material wastage reduction that the Levine patents are directed toward achieving for a large building are virtually irrelevant at the job site. Because the Levine method and apparatus are for producing patterns for fittings for an entire building, and because, therefore, many patterns are produced in batch-wise fashion, slight savings in material for each pattern can be multiplied by a large number to result in considerable savings. However, for customized fittings to be created one at a time at a job site, no such considerable material savings can be obtained. On the contrary, at a job site, the time that would be wasted to make small savings in material would be much more costly than the small value of the material savings obtainable.
Although it is not practical to waste a lot of time at a job site to make small savings in material, it would be desirable to be able to make use of the scrap pieces of sheet metal so that they are not in fact wasted.
Aside from lacking efficiency and lacking practicality of sheet metal pattern making at a job site, the prior art does not provide for computerized pattern making for a number of specific fittings that are important in ductwork. For example, although the Levine patents provide for pattern making for radius throat, radius elbows, Levine does not provide pattern making for square throat, radius elbows. Furthermore, the prior art provides for making only 90 degree elbows. None of the prior art provides for making 0-90 degree radius elbows.
It would be desirable, therefore, to have a computerized pattern maker that can provide for elbows having an angular degree range all the way from 0-90 degrees.
Furthermore, none of the prior art provides a computerized pattern layout apparatus that lays out patterns for boxes, for plenums for diffuser boots, for two-piece radius elbows, sled boots, transitional 0-90 degree radius elbows, transitional 0-90 degree double radius elbows, transitional 0-90 degree radius tees, and transitional 0-90 degree double radius tees. It would, therefore, be desirable to have a computerized pattern maker that provides patterns for boxes for plenums, for diffuser boots, for two-piece radius elbows, sled boots, transitional 0-90 degree radius elbows, transitional 0-90 degree double radius elbows, transitional 0-90 degree radius tees, and transitional 0-90 degree double radius tees.
Other prior art references known to the applicant are as follows:
______________________________________ Inventor(s) Patent No. ______________________________________ Gerber et al 3,477,322 Goodstal et al 3,843,875 Korelitz et al 3,867,616 McFadden et al 3,875,389 Cox et al 3,927,948 Weber 4,152,765 Rosenthal et al 4,181,954. ______________________________________